The invention relates generally to wells for the production of petroleum products and specifically to methods and systems for avoiding damage to behind-casing structures.
Wells for the production of petroleum products are drilled through the earth""s subsurface. Thereafter, a well may be lined with a casing and/or other liner and cemented to permanently fix the casing in the wellbore. The casing and/or liner that lines the wellbore is typically made from a plurality of sections that are coupled together by any suitable means, such as by threaded connections.
Downhole equipment for monitoring the production of hydrocarbons in a well or for monitoring the displacement of fluids in the surrounding formation may be permanently installed in the well. Cables for power and/or signal transmission usually connect the downhole equipment with equipment at the earth""s surface. In some cases, the cabling may be positioned on the outer surface of the casing. In other cases, the cabling may simply lie between the casing and the wellbore wall. In either case, once cementing occurs, the cabling and the downhole equipment will be permanently fixed in the well.
At some point during the life of a well, it may be desired to change the trajectory of the well after the casing has been cemented into place. Moreover, it may be desired to drill and complete one or more lateral branches after the casing has been set in place. Horizontal or lateral wellbores are desirable because they maximize the wellbore""s presence in a productive part of a formation. Thus, lateral branches are advantageous in that they may increase the production of petroleum products from a parent well. Accordingly, one or more lateral wellbores may be drilled at various depths along the parent well. If one or more lateral wellbores are planned for a particular well, casing string installation may be complicated by the need to orient the casing in a desired azimuth for drilling or milling while avoiding an azimuth that will sever the cabling that is positioned behind the casing.
Requiring that the casing be oriented during assembly to ensure that a lateral branch can be drilled at an azimuth that does not interfere with the behind-casing cabling increases the cost associated with installing the casing.
In general, according to one embodiment, the location of a structure behind a casing in a wellbore is determined with respect to an element inside the casing. Thereafter, a position on the casing that is away from the area proximate the location of the structure is identified. An opening may then be cut in the casing at the position to avoid damaging the structure.
Other or alternative features will become apparent from the following description, from the drawings, and from the claims.